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15 pages, 4892 KiB

Open AccessFeature PaperArticle

The Long-Term Mitigating Effect of Horizontal Ground-Source Heat Exchangers on Permafrost Thaw Settlement

by Amir Fatollahzadeh Gheisari, Pooneh Maghoul, Hartmut M. Holländer, Rob Kenyon, Rob Sinclair and Maryam Saaly

Processes 2021, 9(9), 1636; https://doi.org/10.3390/pr9091636 - 10 Sep 2021

Cited by 4 | Viewed by 2315

Abstract

This study investigated the long-term effect of horizontal Ground-Source Heat Exchangers (GSHEs) on mitigating permafrost thaw settlement. In the conceptual system, a fan coil was used to chill the recirculating fluid in the linear High-Density Polyethylene (HDPE) ground loop system. A fully coupled thermo-hydro-mechanical finite element framework was employed to analyze multiphysics processes involved in the thaw settlement phenomenon. To investigate the sustainability of the system, a period of 50 years was simulated. Two operational modes were defined: one without and the other with HDPE. Different heat carrier velocities and inlet temperatures, and heat exchanger depths were examined to explore their effects on the thaw settlement rate. It was concluded that the proposed system can effectively alleviate the predicted permafrost thaw settlement over the study period. Moreover, the heat carrier temperature was found to have a prominent impact on the thaw settlement rate amongst other parameters. Full article

(This article belongs to the Special Issue Numerical Modeling in Civil and Mining Geotechnical Engineering)

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14 pages, 2382 KiB

Open AccessArticle

Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

by Pavel Neuberger and Radomír Adamovský

Energies 2019, 12(10), 1853; https://doi.org/10.3390/en12101853 - 15 May 2019

Cited by 7 | Viewed by 3061

Abstract

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m² and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m²·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m²/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters. Full article

(This article belongs to the Special Issue Sustainable Energy Reviews)

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16 pages, 8247 KiB

Open AccessArticle

Suggestion of a Scale Factor to Design Spiral-Coil-Type Horizontal Ground Heat Exchangers

by Jun-Seo Jeon, Seung-Rae Lee, Min-Jun Kim and Seok Yoon

Energies 2018, 11(10), 2736; https://doi.org/10.3390/en11102736 - 12 Oct 2018

Cited by 10 | Viewed by 3293

Abstract

Spiral-coil-type horizontal ground heat exchangers (GHEs) have been increasingly used in ground source heat pump (GSHP) systems due to their higher heat transfer performance. Many attempts have been made to investigate the heat transfer mechanism and establish design methods for the spiral-coil-type ground heat exchangers. Nevertheless, a universal design method for horizontal GHEs has not been reported due to its complexity. In contrast to the spiral-coil-type horizontal GHEs, straight-line-type horizontal GHEs have been widely adopted since they are easy to design for use in industry. In this study, a scale factor model, which could be used to design the coil-type exchanger based on the design length of a straight-line-type heat exchanger, was presented. The ratio of the mean thermal transfer energy between the straight-line-type and spiral-coil-type heat exchangers was numerically investigated by considering weather condition, configuration of GHE, and thermal properties of the ground. Using the numerical results for a total of 108 cases, artificial neural network and linear regression methods were employed for the model development. The proposed model of the scale factor may provide an alternative way to design the spiral-coil-type horizontal GHEs. Full article

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16 pages, 5539 KiB

Open AccessArticle

Study of Ground Heat Exchangers in the Form of Parallel Horizontal Pipes Embedded in the Ground

by Krzysztof Neupauer, Sebastian Pater and Krzysztof Kupiec

Energies 2018, 11(3), 491; https://doi.org/10.3390/en11030491 - 26 Feb 2018

Cited by 9 | Viewed by 3089

Abstract

In order to predict long-term changes in the temperature of the ground in which a horizontal ground heat exchanger has been installed, it is beneficial to implement simplified mathematical models of heat transfer. The possibility of using a one-dimensional equation of heat conduction while modelling heat transfer in a ground heat exchanger with horizontal pipes has been demonstrated in the work. A theoretical analysis based on the linear heat source model as well as experimental research works have been carried out. It has been concluded that the temperature profiles of the ground in which parallel pipes of the heat exchanger are placed do not significantly differ from the profiles for the heat exchanger in the form of a plate; in particular, this refers to large distances from the level in which the pipes are positioned, small distances between pipes axes and the long duration of the process. Discrepancies between the calculated temperature increases for pipe and plate exchangers varied significantly in the individual time intervals, and were approx. 20–30%. The conducted experiments have demonstrated that the temperature field around parallel pipes of the heat exchanger may be described by the linear heat source model. The compatibility of temperature maps that were determined theoretically and experimentally was satisfactory with a good degree of accuracy. Full article

(This article belongs to the Section L: Energy Sources)

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14 pages, 2402 KiB

Open AccessArticle

Analysis of the Potential of Low-Temperature Heat Pump Energy Sources

by Pavel Neuberger and Radomír Adamovský

Energies 2017, 10(11), 1922; https://doi.org/10.3390/en10111922 - 21 Nov 2017

Cited by 7 | Viewed by 3936

Abstract

The paper deals with an analysis of temperatures of ground masses in the proximities of linear and slinky-type HGHE (horizontal ground heat exchanger). It evaluates and compares the potentials of HGHEs and ambient air. The reason and aim of the verification was to gain knowledge of the temperature course of the monitored low-temperature heat pump energy sources during heating periods and periods of stagnation and to analyse the knowledge in terms of the potential to use those sources for heat pumps. The study was conducted in the years 2012–2015 during three heating periods and three periods of HGHEs stagnation. The results revealed that linear HGHE had the highest temperature potential of the observed low-temperature heat pump energy sources. The average daily temperatures of the ground mass surrounding the linear HGHE were the highest ranging from 7.08 °C to 9.20 °C during the heating periods, and having the lowest temperature variation range of 12.62–15.14 K, the relative frequency of the average daily temperatures of the ground mass being the highest at 22.64% in the temperature range containing the mode of all monitored temperatures in a recorded interval of [4.10, 6.00] °C. Ambient air had lower temperature potential than the monitored HGHEs. Full article

(This article belongs to the Section L: Energy Sources)

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13 pages, 2837 KiB

Open AccessArticle

Monitoring and Analysing Changes in Temperature and Energy in the Ground with Installed Horizontal Ground Heat Exchangers

by Pavel Pauli, Pavel Neuberger and Radomír Adamovský

Energies 2016, 9(8), 555; https://doi.org/10.3390/en9080555 - 28 Jul 2016

Cited by 9 | Viewed by 4159

Abstract

The objective of this work was to monitor and analyse temperature changes in the ground with installed linear and Slinky-type horizontal ground heat exchangers (HGHEs), used as low-potential heat pump energy sources. Specific heat flows and specific energies extracted from the ground during the heating season were also measured and compared. The verification results showed that the average daily ground temperatures with the two HGHEs are primarily affected by the temperature of the ambient environment. The ground temperatures were higher than ambient temperature during most of the heating season, were only seldom below zero, and were higher by an average 1.97 ± 0.77 K in the ground with the linear HGHE than in the ground with the Slinky-type HGHE. Additionally, the specific thermal output extracted from the ground by the HGHE was higher by 8.45 ± 16.57 W/m² with the linear system than with the Slinky system. The specific energies extracted from the ground over the whole heating season were 110.15 kWh/m² and 57.85 kWh/m² for the linear and Slinky-type HGHEs, respectively. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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